The overall objective of this research project is to investigate biochemical changes that occur in the uterus during implantation. The approach is to define specific biochemical events associated with the transformation and proliferation of uterine decidual cells. The role of hormones in preparing the uterus for decidualization will also be pursued by attempting to correlate the occurrence of these biochemical events with the hormonal preparation of the uterus. Prostaglandin levels (E and F2 alpha) will be measured in the uterus following oil stimulation of a decidual cell reaction (DCR). The role of histamines in the DCR will be investigated using antihistamines, histamine depleters and by direct administration of histamines. RNA polymerase activities in isolated uterine nuclei will be measured following stimulation of a DCR.